Electromagnetic transducer head



Jan. 2, 1951 c s 2,536,030

ELECTROMAGNETIC TRANSDUCER HEAD Original Filed Dec. 5, 1946 F? qJ F? q. 2 W /l 5g J5 #4 ME/475' Patented Jan. 2, 1951 ELECTROMAGNETIC TRANSDUCER HEAD Marvin Camras, Chicago, Ill., assignor to Armour Research Foundation of Illinois Institute of Technology, Chicago, 111., a corporation of Illinois Original application December 5, 1946, Serial No; 714,286. Divided and this application June 6,

" I 1947, Serial No. 752,989

13 Claims. (Cl. 179- 1002) This invention relates to a magnetic recorder method and means, and more particularly, to a particularly eifective structure for an electromagnetic head and to a novel method of magnetically recording fluctuating electric energy on a traveling record member and reproducing a ma netic recording from a traveling previously magnetized record member.

The particular novel electromagnetic head structure and the particular novel magnetic recording and reproducing methodhe're'in described and claimed has been found to be particularly effective in making a magnetic record on a moving picture film and reproducing the magnetic record therefrom.

One of the biggest problems in connection with making a magnetic record on a moving picture film lies in getting a sound track which is sufficiently large so as to enable a sufiicient amount of energy to be recorded on the film without changing the conventional dimensions of the film. This diificultyhas been extremely great in connection with 8 millimeter and 16 millimeter moving picture film.

One of the principal objects and features of the present invention is to provide a novel electromagnetic head for a traveling magnetic record member.

A further object of the present invention is to provide a novel method of magnetically record- ,5

ing and reproducing fluctuating electric energy.

A still further object of the present invention is to provide a novel sound head for an elongated fiat record member, such, for example, as a film or tape.

Another and further object of the present invention is to provide a novel electromagnetic head for a tape record member having a magnetic sound track on two surfaces thereof disposed substantially at right angles to each other.

Another and still further object of the present invention is to provide a novel electromagnetic transducer head having a shoulder portion in the magnetic polar portion thereof over which the record member rides and in which two surfaces at right angles to each other are effective in magnetizing the record member or reproduc ing a record previously magnetically recorded on the record member.

Still another and further object of the present invention is to provide a novel erase head for a magnetic recorder.

This application is a division of my copending application entitled Magnetic Record Member, U. S.-Serial No. 714,286, filed December 5, 1946.

Iii)

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and manner of construction and method of operation, together with further objects and advantages thereof, may best be understood b refer.- ence to the following description, taken in con-.- nection with the accompanying drawing in which:"

Figure 1 is a diagrammatic sketch of apiece of moving picture film; x 1.

- Figure 2 is a vertical sectional view of a'film such as that illustrated in Figure 1 ridin over an oil-damped flywheel and in engagement with an electromagnetic transducer head; and

Figure 3 is a diagrammatic side view of an electromagnetic transducer head and erase head and the film with which they are associated.

As the term will hereinafter be used, electromagnetic head will be used in a generic sense to designate either an erase head, a record head, or a reproducing head, or any combination thereof. The term electromagnetic transducer head will be employed to designate either amagneticrecording or a magnetic reproducing head or both.

While the novel principles of the present invention are not limited to a structure for use on moving picture film only or to a method of recording or reproducing a magnetic record on a moving picture film, they are particularly applicable to such. For that reason, there is illustrated in Figure 1 of the drawing, a moving picture film In which includes a main body portion l I formed of cellulose nitrate or cellulose acetate and is provided with a series of sprocket holes I2 which are located between the picture frames l3 and an edge H of the film l0.

As may be seen best in Figure 2 of the drawing. a magnetic sound track [5 is coated over a portion of the upper surface of the film Ill between the sprocket holes l2 and the edge M as well as around the adjacent corner and down over the edge surface of the film. This gives a substantial surface area for the magnetic sound track without the disadvantage of having to bring the sound track up to the edge of the sprocket holes l2.

As is well known to those skilled in the art, the punching of the sprocket holes I! in the film 10 causes a stressing of the film in the immediate region of the sprocket holes which results in a very bad effect on the magnetic sound track I! when the sound track is brought into this region of stress.

through conductors 25 and 25. "quency biasing coil 24 is preferably connected in series with an erase coil 2.1 which mounted on an erase head 28 similar to the electromagnetic An electromagnetic transducer head is having a pair of polar portions i1 is arranged to ride on the sound track 55 of the film i6. These polar portions li include a longitudinally extendin shoulder portion I3 .having a side wall .35. The shoulder portion 18 is arranged to ride on top of the sound track [5, while the Wall portion 49 is arranged to ride against the portion of the sound track H) which lies over the side edge Hi oi the film ID.

The electromagnetic transducer head It is spring-pressed by means of a leaf spring 26 or other suitable mounting mechanism which is carried on a supporting structure 2!. This spring means 20 resiliently urges the head it against the film as the film i5 rides over aninertiainember 2| mounted for rotation on the axis 22. This inertia member may be an oil-damped flywheel or other suitable stabilizing member or capstan.

The electromagnetic .transducer head as also includes a signal coil 23 and a high frequency "biasing coil 24% which are, respectively, energized Th high fretransducer head it but having a slightly larger spacing between the pole portions 11. The erase head 28 is alsoresiliently mounted on a leaf spring 29 carried on the supporting frame 2!.

It has been found that the above described arrangement and technique .is so emcient that satisfactory results may be obtained even 3 -mmgfilm, notwithstanding the low speed and the many modifications maybe made, and I, therefore, contemplate by the appended claims to 'cover 'allsuch modifications :as .fall within the true spirit and scope of my invention.

I claim as my invention:

1. An electromagnetic transducer head comprising a core having a pair of confronting pole portions and a signal coil mounted on said core, said confronting pole portions .eachhaying a pair of magnetically excitable record member contacting surfaces of a rabbeted side edge of said core,

said surfaces being disposed substantially at right angles to each other.

2. An electromagnetic transducer head includinga pole portion for engagement with a record member, said pole portion having a substantially .L-shape magnetically excitable contacting surface on a side edge of said transducer head so as to be simultaneously engageable with two adjacent sides of a record member.

3. A .demagnetiz'ing head including a pole portion for engagement with a record member, said pole portion having a substantially L-shape magnetically excitable contacting surface so disposed one side edge .of said "pole portion as to be adaptable to simultaneous engagement with two adjacent sides of record members with which it is associated.

MARVIN CAMRAS.

-REFERENCES CITED The foliowing references are of record in the die of this patent:

'UNI'IED STATES PATENTS 

